Here's a quick charette: Build a 432 SF art studio with a 444 SF unfinished ADU above it. Remodel the existing ADU (Casey's Room) as previously imagined. Could we do this for $240,000? 876 SF new (but largely empty, like a garage), 480 SF dense remodel (bath, kitchen, doors, windows). $185/SF for the new studio, flat $77,500 for the ADU remodel. Adds 1,100 SF to the house for a total of 2,700 SF.

Could we get $1.3M? That is, would the remodel pay for itself?

This would be a more comfortable home for me, certainly. I would park the car in the "studio," which I would also use as a workshop. I could use the upstairs future ADU for storage and files (or music), and a south-facing window would make it easy to step out on the roof for maintenance.

The official parking spot as shown would be graded at 260.0 and "paved" with gravel. I could build a deck to match the ones in the rear with a top at 263.0

Another quick sketch went in a Villa Savoye direction, but I realized that the trees argue for verticality and random, not gridded and horizontal like Villa Savoye. Random verticality.

But the exterior cladding is an avenue to explore. I'm imagining a simple flat roof with something like TPO or PVC with an overly-flashed parapet. The studio would basically be a rain screen.

So, large format porcelain tiles become an option, or decorative metal panels. Expensive Schluter frames around cheaper Hardie panels, maybe.

Hardie has new sand finish and seagrass texture, as well as random width vertical siding.

I like a lighter tone (I modeled white limestone in Chief, with warm wood on the corner pop-out--the color consultant wanted warm wood to balance the green house.) But the distinct studio could be black, too. We could do a porcelain tile that's black with depth, for example.

Shou Sugi Bahn effect is cool.

Note: I turned the exposure down on the two black renderings just to see the difference.

Just for fun, I went back to blending in with the existing house. It has advantages; it would be cheaper to build, certainly.

We should probably bring the drip line on the studio up to match the house.

Roof deck over studio

 I want to remember this video by Matt Risinger: Deck Over A Flat Roof (4/13/2018)

The roof is a "bathtub" with drains and scuppers. "We've got some sloping on this deck." (Details would be nice.) Plastic standoffs from Bison hold up a wood deck--they are not physically connected to the deck--no penetrations. The wood deck is 2' x 4' panels.

TPO - Thermoplastic polyolefin. White, reflective, single-ply roofing membrane. Roofonline.com says "PVC roofing is better. TPO is usually somewhat cheaper." 45-mil TPO. Puncture resistance: TPO is tougher than EPDM, but not as tough as PVC.

Ascent Roofing - Single Ply TPO Roof Installation Process Explained (7/15/2022). 1/4" or thicker underlayment in 4x8 sheets. TPO seems like linoleum.

Older: Top 3 Flat Roof Materials Explained - Torch Down, EPDM, TPO - Which is the best? (4/8/2016)

EPDM: .045", .060", .090" - Most use .060" (about as thick as a quarter). It's the cheapest. You need walk mats, because EPDM is so puncture-prone.

TPO: .045" and .060". Seams are heat-welded, not glued. Only been in use since about 2000. Only 15-20 year warranties.

Torch-down is 5 layers, more puncture-resistant. 3/8" thick. Modified bitumen. Over fiberglass liner.

Roofonline.com says single-ply membranes say minimum roof pitch is 1/4" per foot. So, for a 20' wide roof, we need 2.5" on either side of a ridge or valley, or 5" from one side to the other.

ADU Building Permit

One of the 7 Habits is Start with the end in mind. I can't see the finished building, but I can imagine a set of plans. I went to the Seattle.gov/DPD site and got sidetracked looking at PDFs filed for the project across the street at 814, including the site drainage plan and the arborist report. Still no construction plans (I would love to know how they're meeting the insulation requirements).

Returning from the bunny trail, I found Tip 106, the general standards for plans and drawings.

Plan Set submission

• Must be PDF, max size 500MB, 300 ppi, all sheets in one file (supporting material in other PDFs), landscape.
• Retain bookmarks, if possible
• Flattened--not sure what that means. Also, remove ACAD.SHX and other objects in Acrobat's Tools>Comments view. Again, huh?
• "Full size"--WTF? 
• Must be unprotected and unlocked
• No .zip files
• All sheets same size and orientation
• File name must be < 200 characters, no special characters. Should be "Plan Set" for my purposes. ("Approved Plan Set" is reserved.)
• Once approved, I'll have to download the approved file and print it for the record copy at the jobsite.

  

  Seattle DPD example drawing

  
  

Page layout

• Min. sheet size: 11 x 17, min. font size: 10pt
• "Clearly denote the paper sheet size"--What?
• Approval stamp space 4.5"w x 1"h (or 2.5" square) the same on each sheet--lower right corner preferred, title block or drawing space. 
• Architect's stamp goes in title block.
• Scale must be specified and graphically depicted. Min. scale 1/4"=1'0" (1/8 for large projects)

Tip 103 covers site plan requirements and Tip 103A covers site plan guidelines. I think I'm in an Environmentally Critical Area, so I need Tip 103B, ECA site plan requirements, too.

• We're talking about a Basic Site Plan (Enhanced is only required for new projects.)
• Checklist of required info:
• Scale (minimum 1" = 10')
• Address of project
• Owner's name
• Legal desc (incl easements, with King Co. recording number)
• Assessor's parcel number
• North arrow--must point up and be consistent across all sheets
• Property lines, dimensions, and bearings
• Dimensions and ROW limits for all streets. Note type: asphalt, concrete, gravel
• Curbs, sidewalks, street trees--type, location, dimensions
• Boundaries of steep slopes, steep slope buffers and other ECA areas
• Primary path to each dwelling unit
• Location and dimensions of all driveways, parking areas and other paved areas (existing and proposed)
• Existing and proposed structures: buildings, rockeries, decks, porches, patios, driveways.
• Front, rear and side dimensions to property lines and between structures
• If subject to SMC 25.11 (and I think I am):
• Location, species, diameter at 4.5' above ground of all trees, including any that overhang or have roots into my lot.
• Tree protection area for all trees that will be retained
• Tree protection fencing. Include SDCI Tree and Vegetation Protection Detail.
• Site lot coverage calculations
• Clearly distinguish between existing and proposed ("Existing wall to remain" is good).
• Window wells, chimneys, etc.--location and dimension
• Center elevation at 25' intervals if a change to access or parking is proposed.
• Existing and finished grade elevation of driveway at property line and at garage entry, if a change is proposed. Curb cuts note does not apply.
• Identify all physical restrictions to site access (utility poles, rockeries, street trees).
• Only required for Enhanced site plans (multi-unit, commercial):
• Contour lines 2' intervals. Identify culverts. 
• Sewer mains (PPS), storm drains (PSD)
• Water mains, fire hydrants, water meters. Power poles, street lights, street signs.
• Calculations demonstrating compliance with applicable Land Use Code dev stds.